I recommend the Kensington trackball for graphics work, which assume a very precise pointing, we get a better score than a mouse. The wheel allows scrolling in windows without ever moving the hand, eliminating pain in the elbow after prolonged use. To drag & drop it is very difficult to do with one hand, in fact if it remains supported thumb (and it must support relatively strong) then we contracted out and it is very difficult to maintain the accuracy on the ball. This is undoubtedly a problem of all trackball; I circumvents it by drag & drop to 2 hands: click of the left index finger, while the right hand only handles the ball. For graphic work is a very good pointing device, is accustomed to it quickly and it would not matter to me regain a mouse! By cons, for word processing and the small office the mouse is a more natural use. The two are not exclusive, on my PC I kept mice and trackball, the whole family is thus happiness.
